Given that 1) the PA system is highly sensitive to spatial mismatch, i.e., the RA could not reach the same point as the PA; 2) The PA system does not have analytical model to obtain tractable evaluations, recent studies [1]}, [2]}, [3]}, [4]}, [5]}, [6]}, [7]} address these problem and further clarify the potential of the PA system. [1]} investigates the spatial mismatch problem in the PA system, and proposes a tractable channel model to evaluate the effect of spatial variation with rate adaptation. Then, the model in [1]} has been further evaluated in [2]} with temporal evolution of the channel. With two sets of antennas on top of a vehicle, the potential of involving PA partially into the transmission have been studied in [3]}, [4]}, where HARQ is combined with system and optimal power [3]} and average rate [4]} of the HARQ-based PA system are investigated respectively. Considering finite block-length transmission, [5]} studies the effect of the codeword length on the average throughput and error probability. Also, [6]} reviews the recent progress on the PA study and proposes adaptive/non-adaptive delay methods to be applied in the PA system with spatial mismatch. The role of the PA in the development of MR and IAB are also summarised. Finally, [7]} extends the PA concept to multiple vehicles and investigates the potential of using PA for dynamic blockage avoidance in cooperative internet-of-vehicle networks.
